1. Field of the Invention
This invention relates to an improvement of footgear, and more particularly to an improvement of the construction of a footgear sole.
2. Description of the Prior Art
Conventionally, there have been proposed various kinds of footgear in an attempt to facilitate well-balanced walking, which, however, have been unsuccessful. It is essential to perform right or proper walking in order to prevent diseases and to maintain good health of human beings. The right and well-balanced walking of human beings stems from assuming a standing position. In other words, to vertically stand on a horizontal plane against the gravity is the essential factor in right walking. To this end, the bottoms of feet of a human being, which function as a base of the standing position, must be placed on the horizontal plane. The right and well-balanced walking causes mixer movement to the pelvis of the human being in a suitable manner, and further the walking transfers tension and relaxation to muscles of legs. The thus transferred tension and relaxation cause a pumping function of blood vessels at lower portions of the muscles to accelerate blood circulation, which leads to good health of the human being. Ideally, to walk barefoot is the best manner of walking. Therefore, in society where human beings essentially wear footgear, the range and function of barefoot movement should be protected to a possible furthest extent. Ideally, the footgear should be formed such that the bottom of the foot and the footgear move in one body during walking.
Conventional footgear, however, has impeded the range and function of the barefoot movement. In the conventional footgear proposed, for example, by U.S. Pat. No. 2,124,986, 2,928,192, 3,662,478, and, U.S. Pat. No. D 189,839, the sole has a raised heel portion. For example, a footgear sole disclosed by U.S. Pat. No. 2,928,192 includes a member having a uniform thickness, however, the sole is provided with an additional member at a heel portion, whereby the entire thickness thereof is not uniform. Similarly, a footgear sole proposed by U.S. Pat. No. 2,124,986 does not have a uniform thickness over the entire area thereof.
Because of the reasons mentioned above, it is difficult to obtain the essential factor in right walking, i.e. "to vertically stand on the horizontal plane against the gravity", by wearing any of the conventional footgear, and therefore right and well-balanced walking cannot be performed. In regard to this point, some of Japanese sandals have the construction with a uniform thickness. Conventional footgear having the uniform thickness, however, can provide only awkward style of walking and is liable to slip out of the foot of the wearer. It is not always correct that footgear having the uniform thickness can provide right walking. To cope with this inconvenience, there may be conceived an idea that comfortable walking is obtained by wearing footgear which is formed of an extremely soft material and liable to be deformed depending on force applied thereto by the foot or by the ground. If the footgear is formed of the material mentioned above, however, unevenness of the ground directly affects the bottom of the foot, whereby the primary function of footgear, i.e. to protect the foot, is damaged. Further, such a soft material has a problem of poor durability.
On the other hand, there is known a footgear sole, for example, from U.S. Pat. No. 3,875,689, which has an almost uniform thickness over the entire area thereof, without raising a heel portion. However, the footgear sole of this type tapers in thickness at a tip portion thereof in an attempt to provide comfortable walking, and therefore the entire sole is not strictly uniform in thickness. As a result, when the wearer of this footgear stands on the horizontal plane in order to assume the essential position for the right walking, he can feel unstable.
In addition, incisions or grooves formed in the conventional footgear sole are provided with a view of a slip stopper, and therefore they do not function to deform the sole as appropriate during walking. For example, the footgear sole disclosed by U.S. Pat. No. 2,124,986 has formed therein slits which exclusively functions as a slip stopper. Therefore, the construction of the slit is not liable to change the sole into a shape suitable for walking.